Core for choke coil or resistor



r Jan.

E. J. KNOUSE CORE FOR CHOKE COIL OR RESISTOR Filed May 4, 1951 INVENTOR.Co/yar Maase.

CORE FOR CHOKE COIL R RESISTOR Edgar J. Knonse, St. Marys, Pa., assignerto Quality Coinponents, Incorporated, St. Marys, Pa., a corporation ofPennsylvania Application May 4, 1951, Serial No. 224,550

1 Claim. (Cl. 336-492) This invention relates generally to cores orforms for coils such as resistor or chokecoils and the like and moreparticularly to the construction of the core itself.

The core of this invention is an improvement over the core or forms asdisclosed in the Hugh N. Veley Patent No. 2,355,611.

The principal object of this invention is the provision of a core orform for choke or resistance coils. These cores are ordinarilyconstructed from plastic insulating material such as glass, porcelain orthermoplastic or thermosetting resins and have leads with their endssecured therein and extending from the core at positions adjacent whichthe coil ends or connections pass.

The problem of locking the coil ends or connections to the core toprevent the coil from accidentally unwinding or shifting in positionwith a resulting change in impedance has long been recognized. When thecore ends are molded with notched ends as disclosed and claimed byVoley, the coil end which is used as a connection is bent over the axialedge of the notch and passes straight to the lead around which it iswound and subsequently soldered. This notch extends almost to the leadand the tendency is to wrap the coil end to the lead at a distance fromthe end of the core as actually shown in Veley. ln production these coilends are caused by the notch to be wound on the lead at a considerabledistance from the end of the core. Such spacing will break the coil endsor coil connections when the leads are exed to apply them to a circuitand thus ruin the coil. if the coil is covered the break in the coil isnot readily detected unless its circuit is checked.

To avoid this difficulty one is required to wind the coil ends orconnections closely adjacent the end of the form so that no amount offlexing of the leads will cause the coil ends to break. This isaccomplished by providing a slot in the end of the core, the bottom ofwhich is spaced from the lead. A slot of this character provideslongitudinal and not axially extending edges and only the crosssectional end of the slot is formed in the end of the core. The coilcannot be properly locked or anchored with this slot unless the wire isdrawn over the bottom of the slot end and then wound on the lead closelyadjacent the end of the core.

If a coil end is wound on the lead in spaced relation to the end of thecore, the coil will not be anchored and will unwind and can be readilycaught by visual inspection before the coils are coated or covered. Thusthe actual position of this simple slot in the core prevents distructionof the coils by the mere flexing of their leads.

Again the slot extending longitudinally of the core may serve two otherpurposes. First, the reception of a plastic that holds the turns of thecoil in place and interlocks the coil with the core. Secondly, the slotor a covered passage longitudinally of the core may be employed toreceive a wire or other type of electrical core member means which iseffective in changing the impedance of the coil. This electrical coremember may extend part way nited States Patent Patented Jan. 1, 1957 ICCin or all the way through the coil and may be varied in size or metalliccontent to change the coil characteristics.

Other objects and advantages appear hereinafter n the followingdescription and claim.

The accompanying drawings show, for the purpose of exemplication withoutlimiting the invention or claim thereto, certain practical embodimentsof this invention wherein:

Fig. l is an enlarged isometric view of a core having two leads and oneslot comprising this invention.

Fig. 2 is an enlarged isometric view of a core having four leads and twoslots.

Fig. 3 is a sectional view of an enlarged core with coil wound thereonand having two electrical core members therein.

Fig. 4 is an enlarged isometric View of a core having two end leads, twocenter leads and an outwardly open slot. f

Referring to Fig. l of the drawing the core 1 has the ends of the leads2 and 3 embedded therein. ln this instance the leads are substantiallyaxially of the core 1. The leads are usually constructed of tinnedcopper wire that may be flexed. Other kind of wire may be employed.

When the coil is to be wound thereon it must Withstand hightemperatures. The core 1 is preferably made of a molded plastic materialsuch as glass, porcelain or other ceramic material having insulatingproperties. Highly iluxing agents can be employed to mold and bake theseceramics without injury to the leads and in some instances the leads maybe inserted after the core is baked.

Thermoplastic or thermosetting resins having insulating properties maybe molded into these core forms if they are not to be subjected to hightemperatures. This type of core is the most popular for high frequencycircuits not involving high temperatures.

ln Fig. 1 the core 1 is provided with the slots 4 and 5 which arerectangular in cross section and preferably a little larger than thewire to be wound into coil form on the core, but the bottom of the slotshould be spaced from the leads as shown. The cross section of the slot5 is shown in the end 6 of the core and the edge of the bottom of theslot is spaced from the lead 3. These slots do not have to be perfectcross sections of squares, rectangulars or trapezoids but their edgesadjacent the end face 6 should be well delined and preferably square.

ln the structure of Fig. 2 the core 10 has four independent leadsinsulated from each other. The leads 11-12 and 13-14 are held insubstantial alignment with each other. Each lead has a slot 15, 16, 17and 18, each slot with its bottom edge spaced from the lead with whichit is to be employed.

ln the structure of Fig. 3 the core 20 has an upwardly open slot 21extending all the way along the core. T he leads 22 and 23 are disposedin the center of the core with their heads 24 embedded in the moldedplastic of the core. The bottom edges of the slot 21 at both ends of thecore require the Wire 25 forming the coil to be kinked or bent thereoveras shown and the coil ends or connections 26 and 27 are closely adjacentthe end faces of the core end are Wound around their respective leads 22and 23. Any amount of iiexing of these leads will not break these coilends.

The slot 21 has the metal core member 28 forced into the bottom thereof.If wedged in tightly it will stay in place, but the Whole coil is dippedinto a plastic such as varnish and baked to form a coating. This coatingalso lls the slots 21 and hardens between the adjacent turns of the coiland tightly adheres to the surface of the core in the slot and thusfunctions as a key or winding form for each wire as indicated at 30 tosecurely lock the coil on the form.

If the single short metallic electric core member 2S does not havesuliicient choke effect, one or more passages 31 extending through thecore may be provided and of suicient size to receive with a press t, theelectric core member 32. The advantage of this core member is that it isspaced from the coil by the core material and may be shoved into thepassage 31 at any deserved distance to give the proper choke eect afterthe coil has been coated or even when in use.

1n Fig. 4 the core 33 has four leads, two end leads 22-23 and two ofwhich are intermediate 34 and 35 for taking off taps of a coil or theends of two tandem coaxial coils. This core has the outwardly open slot21 and the passage 31. The intermediate ends of taps connecting to theleads 34 and 35 do not need winding locking slots.

While, for clarity of explanation, certain embodiments of this inventionhave been shown and described, it is to be understood that thisinvention is capable of many modilcations and many changes intheconstruction and arrangement of patrs may be made therein and certainparts may be employed Without the conjoint use of other parts andwithout departing from the spirit and scope of this invention.

I claim:

A coil comprising a small molded core of plastic material havingterminals embedded therein and extending outwardly therefrom, a coilhaving its turns wound on said molded core, a passage in the form of anupwardly open slot in the surface of said molded core and extendinglongitudinally of the axis of the coil, said coil being wound over saidslot with its ends connected to the respective terminals, a wire snuglyfitting in said slot and spaced from said coil turns to effect theimpedance of the same, and a plastic coating applied in a ilowa'olestate and when hardened to lock said wire in said slot and interlock theunder side of the turns of the coil winding.

References Cited in the tile of this patent

